noun
authorized vehicle; relevant vehicle
Refers to a vehicle that is officially involved in or permitted for a particular operation, such as emergency, construction, or event-related vehicles.
事故現場には関係車両のみが進入できる。
Only authorized vehicles may enter the accident site.
工事関係車両の駐車スペースはこちらです。
Parking for construction-related vehicles is here.
Compound of 関係 (relation, involvement) and 車両 (vehicle). The exact historical derivation is uncertain, but the term is used in modern Japanese to denote vehicles that are officially connected to a specific purpose or operation.